According to an eyewitness, Jackson met with grizzled veteran coach Dunleavy for two hours Friday morning over breakfast at a downtown Chicago hotel.

Jackson is in Chicago for the pre-draft combine. It is believed to be the first job interview he has conducted for the head-coaching position other than Kerr, who spurned Jackson on Wednesday night in a shocker.

An NBA source confirmed the breakfast meeting and said the Brooklyn-raised Dunleavy, who was inducted into the New York City Basketball Hall of Fame, has used elements of the triangle offense during his four NBA head-coaching stints.

Jackson went from a sleek candidate with no coaching experience to one with plenty of mileage on the tires.

Dunleavy, NBA Coach of the Year in 1999 with the Blazers, lost to Jackson’s Bulls as Lakers head coach in the 1991 NBA Finals. Dunleavy has also coached the Bucks, Blazers and Clippers, where he was coach and general manager.

Dunleavy was fired by the Clippers in 2010, after which he sued Donald Sterling’s club for the money left on his contract. An arbitrator ordered Sterling to pay Dunleavy $13 million in 2011.

Dunleavy lives near Jackson in Los Angeles and they have lunch occasionally, according to the NBA source. But the source said the meeting was more than a friendly get-together.

Dunleavy played a facsimile of the triangle as a player with the Rockets. A source close to Dunleavy said it’s unclear if he’ll be considered a strong candidate.

“Phil doesn’t have a formal candidate list yet because he thought he had a done deal,’’ one person close to Jackson said. “He’s starting from scratch.’’

As The Post reported, Jackson has expanded his coaching search to include more than just triangle specialists, with Mark Jackson on the list.

Jackson was to meet with Knicks GM Steve Mills on Friday to further discuss names and create a list.

Derek Fisher, the former Laker and master of the triangle offense, is considered a prime candidate whenever he’s done playing. But he’s ready to start the Western Conference finals on Monday as backup point guard for Oklahoma City. Fisher, who will retire after this season, has said on record he isn’t interested in coaching next season, but one Fisher confidant said the right situation could make him change his mind.

The Lakers likely will pursue Fisher if they still have an opening. Lakers GM Mitch Kupchak told The Post he hasn’t conducted any interviews yet and the search could drag until draft time.

“We hope to have a coach in place as soon as possible, but we’re not going to rush,’’ Kupchak said. “It’s nice to have something in place by the draft. It doesn’t necessarily have to be the case. We really haven’t begun the process and there’ll be several interviews.”

Asked if the NBA playoffs will affect the search, Kupchak said: “Maybe, maybe not. It’s always good to have a coach in place by the draft. We may. We may not.’’

Kurt Rambis, longtime Lakers assistant, is considered a Jackson disciple, but Kupchak said the Knicks haven’t requested permission to speak to him. There’s speculation Jackson could be enticed into speaking with Fred Hoiberg, the Iowa State coach and former Tyson Chandler teammate who ran the triangle under Tim Floyd with the Bulls.

Because of the Dunleavy meeting, Jackson did not show up at the Chicago gym where the draft prospects were doing workouts. There was speculation he didn’t come to avoid the media. Mills was there, along with new adviser Clarence Gaines, personnel director Mark Warkentien and scouts Mark Hughes and Walker Russell.

Mills said he couldn’t comment on the Kerr snub. Jackson would have had his man had Stan Van Gundy accepted the Warriors’ job instead of choosing to be president and coach of the Pistons.

On hand in Chicago, Van Gundy told The Post: “Everybody’s decision affected everybody else’s decision. But from the minute I talked to ownership in Detroit, I was focused on the Detroit job.’’

Van Gundy could have been turned off by Golden State’s handling of Mark Jackson, a dear friend of his brother, Jeff Van Gundy.

“He’s real close to Jeff,’’ Stan Van Gundy said. “I respect him as a person and what he did in Golden State.’’

Mark Jackson is still friends with assistant GM Allan Houston, and Mills was with the Knicks when Jackson finished runner-up to Mike D’Antoni for the coaching job in 2008.